The invention relates to an air-laid non-woven web of cellulose fibers or of cellulose fibers mixed with synthetic fibers having a structure obtained by hydroentangling the fibers to a coherent web, and also a method and a plant for producing such web.
Hydroentangled webs of this kind are to a great extent used for the manufacturing of disposable non-woven products of which can be mentioned,
absorbent core material for feminine hygiene articles,
incontinence articles,
diapers,
table top napkins,
hospital products such as bed protection sheets,
wipes, and
towels.
During the hydroentangling process jets of water are, under the influence of a pressure as high as e.g. 100 bar, directed through a number of nozzles towards a layer of fiber fluff which is air-laid by means of a forming head per se. During the hydroentangling process the fluff is conventionally supported by a base web, which in its turn is supported by a wire.
The base web has to be strong enough to withstand the heavy load from the water jets and is therefore normally produced of synthetic fibers.
In some cases the base web can be supplied to the forming head in form of a spunbonded/meltblown (SMMS) web, but usually it is formed of carded fibers which are hydroentangled and dried before being used as base for the air-laid fiber fluff during the hydroentangling of this.
The carding of the synthetic fiber material is a relatively slow process causing therefore a limitation to the production rate of the total plant.
Besides, the price of synthetic fibers can e.g. be about three times the price of cellulose fibers. The base web therefore is rather costly.
A finished web of 60 g/m2 will typically consist of a base web of 30 g/m2 supplied with a layer of cellulose fibers of 30 g/m2. Such a web has, in relation to its high price, poor absorption properties as the costly synthetic fibers do not or only negligibly participate in the absorption process.
The total weight of a conventional web is typically between 20-60 g/m2 with a base web of between 10-30 g/m2 and air-laid cellulose fiber and/or cellulose fibers and synthetic fibers of between 10-30 g/m2. The webs are relatively thin, for example about 0.5-0.6 mm.